1. Field of the Invention
This invention is related to a portable tool and, more particularly, to a hand portable magnetic reset tool, particularly adapted for use in selectively resetting electromagnetic indicators or the like.
2. Description of the Prior Art
In industry, conventional binary magnetic indicators of the electromagnetic type provide for non-illuminated contrasting color displays. Such electromagnetic indicators find utility in a wide variety of installations. For example, aircraft and portable electronic equipment. Normally, they are preferred over the typical illuminated indicators, such as those using glow tubes or bulbs, especially wherein the ambient light conditions make it difficult to distinguish the display from the surrounding background.
Ordinarily, these prior art electromagnetic type indicators are characterized by a rotatably spherical magnetic indicator member that has discrete opposite magnetic poles, a latching magnet that serves to latch the indicator member in a position, and an energizing coil adjacent the latching magnet and spherical magnetic indicator member. Upon energization of such coil, a magnetic field will be created which causes the latching magnet and the spherical magnetic indicator to rotate to a reversed position. Resetting of the electromagnetic indicator, i.e., making the spherical indicator return to its original position may be accomplished by introducing an overriding magnetic field which is sufficient to unlatch and reposition the indicator member.
One prior art approach for resetting the electromagnetic indicators is accomplished by moving the electromagnetic core of such indicator into close proximity with a strong permanent resetting magnet that is located in line with the electromagnet so as to induce in the core thereof a magnetic field opposite to the field induced therein by the energizing coil. The resulting magnetic field is of sufficient strength to reverse the position of the indicator member. Such approach, however, has certain drawbacks in that it is necessary that the resetting magnet be isolated from the coil and its core until such time as the indicator is to be reset. This normally requires maintaining a relatively large gap or space between the electromagnet and the resetting magnet. The gap, however, results in relatively long, less compact, indicator housings. Moreover, the aforedescribed construction is somewhat expensive to manufacture and is somewhat more complicated in structure by virtue of the necessity to have a permanent magnet associated with each of the electromagnetic cores for the respective electromagnetic indicators.
Another prior art approach to reset conventional electromagnetic indicators is accomplished through an auxilliary permanent magnet which is movably mounted on a fixed panel adjacent the indicator and arranged to operatively cooperate with an extension that projects out of the indicator housing in the path of movement of the resetting permanent magnet. A shield device is provided for shielding the resetting magnet and holding it away from the core extension to which such projection is operatively connected. At such time it is desired to reset the indicator, the resetting permanent magnet is moved toward the core extension. As the gap between the resetting magnet and core extension is diminished, the resetting magnet induces in the electromagnetic core a magnetic field which overrides the magnetic latching and causes the spherical indicator member to rotate back to its original position. This latter approach, as with the preceding, results in certain shortcomings, foremost among which is the necessity to provide each electromagnetic indicator operatively connected to a panel with a permanent magnet as well as a core extension member which operatively cooperates between the electromagnetic core and the permanent magnet. It is obvious, therefore, that this particular form of construction is relatively complicated in its arrangement not to mention being somewhat expensive in its construction.